Serena Williams of the US chases down a forehand to Carla Suarez Navarro of Spain at the US Open tennis championships in New York, Sept 3, 2013. [Photo/Agencies]

NEW YORK - Defending champion Serena Williams walloped Spain's Carla Suarez Navarro 6-0 6-0 to race into the semifinals of the US Open on Tuesday.

Top seed Williams served up the dreaded "double-bagel" in a quick-fire 52 minutes to set up a clash with fifth seed Li Na, who earlier became China's first US Open semifinalist by beating Russian Ekaterina Makarova.

"Honestly she's a great player," said Williams, blaming windy conditions for the Spaniard's plight on her 25th birthday.

"The conditions today were so tough. It was not her best tennis today."

The outcome may have been more about the world number one being at something close to her best, however.

Williams won 88 percent of her first serves, rifled in four aces, smacked 20 winners to three for her opponent, and won 53 points to just 18 for the 18th seed.

"I played really good. I was just more focused than anything," she added, stopping short of calling it her best. "I like to believe there is room for improvement."

It was only the second love-love victory in a US Open women's quarterfinal dating back to 1968, and first since Martina Navratilova subjected Manuela Maleeva of Bulgaria to the same embarrassment in 1989.